One Indian friend taught me it's something like 'city/see thee gar bah' where the 'k' is silent like the word 'kṣatriya' (the class/caste of the warriors in Indian social order) is 'sat tree ya'. Then again until a professor in Sanskrit comes along....Sigh if only vinodh or Ven Huifeng was online...

It does sound like "shitty" with a "k" sound before it, only the "y" in shitty would be the same sound as the i in shit. Because of that, I usually pronounce it as "sɪtigɑːbə" in casual use (due to accent). Pronouncing it in say, a mantra (such as Oṃ Kṣitigarbha bodhisattva yaḥ), I'm more faithful to the pronunciation though.